1. Field of Invention
The present invention relates to the field of automobile safety and relates more particularly to a safety device intended to protect an occupant of a motor vehicle in a collision.
2. Description of Related Art
For about the last thirty years it has been proposed that the gas-generating systems be incorporated into motor vehicles to inflate conventional textile airbags intended to protect the face and torso of motor vehicle occupants in order to limit as far as possible the risk of bodily injury to which these occupants are exposed in the event of a frontal or side impact. Sometimes, as described for example in German patent application DE 41 16 880, the interior surface of these bags is even coated with a pyrotechnic lacquer.
Recently, in addition to these conventional protective devices, car manufacturers have wished to incorporate numerous safety devices aimed, on the one hand, at protecting the lower limbs of the occupants and at reducing the risk of submarining and, on the other hand, at strengthening the actual structure of the vehicle. In this type of application, the safety devices have to operate in extremely short spaces of time and it is therefore necessary to employ highly efficient pyrotechnic charges which, in very short spaces of time, generate the necessary volume of gas. These gases are often toxic and are often at a very high temperature. Conventional textile airbags must therefore not be used because they are liable, on the one hand, to be damaged by the very hot gases and, on the other hand, because of their porosity, to allow the toxic gases to pass into the cabin of the vehicle.
To alleviate this problem, safety devices each comprising a conventional gas generator connected to an impervious inflatable metal bag via a gas duct have therefore been proposed, as described in U.S. Pat. No. 5,615,914 and U.S. Pat. No. 5,839,756. However, the use of a gas generator as a separate component makes these safety devices bulky overall and too heavy, making them difficult to incorporate in great number into a vehicle.
The person skilled in the art is therefore still in search of a compact and lightweight safety device which will allow the use of highly efficient pyrotechnic charges.
The object of the present invention is to answer this problem and the invention therefore relates to a safety device housed in a motor vehicle and which comprises:
i) an impervious inflatable metal bag fixed to a support,
ii) a pyrotechnic charge,
iii) an ignition device intended to be connected to a source of electrical current, characterized in that,
iv) the impervious inflatable metal bag consists of a first metal sheet which has a central orifice, an intermediate fixing zone attached to the support and a peripheral fixing zone and of a solid domed second metal sheet which has a peripheral fixing zone, the two metal sheets being fixed together at their peripheral fixing zone,
v) the pyrotechnic charge is contained in the impervious inflatable metal bag.
As a preference, the support consists of a cylindrical body having a flat top surface to which the first metal sheet of the impervious inflatable metal bag is fixed. This body may moreover be made using two distinct elements, the first element corresponding to the bottom part of the said body and the second element consisting of a plate attached to the said first element.
Also as a preference, a perforated piece, contained in the impervious inflatable metal bag and fixed into the flat top surface of the cylindrical body, holds the pyrotechnic charge in place.
According to a first preferred alternative form of embodiment, the pyrotechnic charge is produced in the form of at least one flat sheet, the said flat sheet being wedged between the perforated piece and a spring, itself bearing against the flat top surface of the body.
According to a second preferred alternative form of embodiment, the pyrotechnic charge consists of loose powder.
Advantageously, the pyrotechnic charge consists of a composite pyrotechnic composition comprising a silicone binder and an inorganic oxidizing charge, such as a mixture of ammonium perchlorate and sodium nitrate, for example.
According to a first preferred embodiment of the invention, the cylindrical body has a radial opening itself extended by a central recess located facing the central orifice borne by the first metal sheet.
According to a first alternative form of the first preferred embodiment of the invention, the ignition device, which consists of an electropyrotechnic igniter itself inserted into an electrical connector, is fixed into the radial opening of the cylindrical body.
According to a second alternative form of the first preferred embodiment, the ignition device consists of a pyrotechnic transmission cord and of a pyrotechnic relay charge. Advantageously, the pyrotechnic relay charge is housed in the radial opening borne by the cylindrical body, and the pyrotechnic transmission cord has one end inserted in the said radial opening and in contact with the pyrotechnic relay charge.
A safety device as described in this first preferred embodiment of the invention is very compact because, at rest, the maximum height of the said safety device corresponds only to the sum of the height of the body and of the maximum distance separating the first metal sheet from the solid domed second metal sheet.
According to a second preferred embodiment of the invention, the cylindrical body consists of a discoid plate which has a side wall, there being, passing through the said discoid plate, a radial channel which starts in the said side wall and ends in at least two widened terminations in the flat top surface. It may prove necessary to increase the number of widened terminations depending on the mass of the pyrotechnic charge employed.
As a preference, the radial channel contains two electrodes which conduct electrical current and each of the two widened terminations of the radial channel contains an ignition bead electrically connected to the two electrodes.
A safety device as described in this second preferred embodiment of the invention is even more compact because the body is in fact reduced to a discoid plate of small thickness.
In general, it may be advantageous to place seals between the first metal sheet and the flat top surface of the cylindrical body.
The present invention also relates to the use of one or more safety devices as described hereinabove:
at the front of the seat part of a passenger seat to raise this passenger in the very first moments following a collision, which makes it possible to greatly reduce the risk of submarining,
in the bottom part of the dashboard so as to protect the lower limbs of the front-seat passengers of the vehicle in a collision,
to strengthen certain parts of the structure of the vehicle in a collision, for example the bumpers and/or the side doors.